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Types of User Defined Functions There are three different types of User Defined Functions. Each type refers to the data being returned by the function. Scalar functions return a single value. In Line Table functions return a single table variable that was created by a select statement. The final UDF is a Multi-statement Table Function. This function returns a table variable whose structure was created by hand, similar to a Create Table statement. It is useful when complex data manipulation inside the function is required. Scalar UDFs Our first User Defined Function will accept a date time, and return only the date portion. Scalar functions return a value. From inside Query Analyzer, enter:   CREATE FUNCTION dbo.DateOnly(@InDateTime datetime) RETURNS varchar(10) AS BEGIN         DECLARE @MyOutput varchar(10)         SET @MyOutput = CONVERT ( varchar(10) ,@InDateTime,101)         RETURN @MyOutput END To call our function, execute: SELECT dbo.DateOnly( GETD

Advantages of User Defined Functions Before SQL 2000, User Defined Functions (UDFs), were not available. Stored Procedures were often used in their place. When advantages or disadvantages of User Defined Functions are discussed, the comparison is usually to Stored Procedures. One of the advantages of User Defined Functions over Stored Procedures, is the fact that a UDF can be used in a Select, Where, or Case statement. They also can be used to create joins. In addition, User Defined Functions are simpler to invoke than Stored Procedures from inside another SQL statement. Disadvantages of User Defined Functions User Defined Functions cannot be used to modify base table information. The DML statements INSERT, UPDATE, and DELETE cannot be used on base tables. Another disadvantage is that SQL functions that return non-deterministic values are not allowed to be called from inside User Defined Functions. GETDATE is an example of a non-deterministic function. Every time th